> I could imagine a future where every house has something like this partially heating their water and air before the real heating system is applied. This is r

> I could imagine a future where every house has something like this partially heating their water and air before the real heating system is applied. This is really important. Where I live - Oslo, Norway - we have a sun thermal collector-thingy[0] on the roof which _aids_ in heating up other stuff. Surely, it needs to be a fire nearby to heat the water enough to have a comfortable shower, but we save approx. $20K yearly[1] on energy costs with this solution. [0] https://en.wikipedia.org/wiki/Solar_thermal_collector https://en.wikipedia.org/wiki/Solar_thermal_collector [1] I live in a housing association with 60 other families in the same building, so needless to say the savings would be a lot less if I lived on my own in one house. :)